Several F-16 warplanes loaded with bombs took off from an air base in southeastern city of Diyarbakir, private Dogan news agency and local reporters said.

Earlier, Turkish artillery units were shelling rebel positions as late as Tuesday night in northern Iraq, according to a government official who spoke on condition of anonymity because he was not authorized to speak to the media.

The strikes were in retaliation for a rebel ambush on Sunday that killed 12 soldiers and apparently led to the capture of eight.

No cease-fire
Turkey, which has massed troops on the border, had warned Iraq and Western allies on Tuesday that an attack was imminent unless the U.S.-backed government in Baghdad takes action. Officials also said there would be no cease-fire with the separatist fighters.

Turkish leaders face growing demands at home to stage an offensive in northern Iraq, where the rebels of the Kurdistan Workers’ Party — the PKK — rest, train and get supplies in relative safety before returning to Turkey to conduct attacks.

Foreign Minister Ali Babacan, returning late Tuesday from meetings in Baghdad, said: “We said that we are expecting them to come with concrete proposals ... otherwise the visit will have no meaning.”
Video: Border tension

The United States issued its most direct demand yet for anti-rebel measures from Iraqi Kurds who hold effective autonomy over territory where Turkish Kurd guerrillas have camps.

Iraqi Prime Minister Nouri al-Maliki on Tuesday ordered the closure of all offices belonging to the PKK in Iraq and said they would not be allowed to operate in Iraqi territory.

'Need more than words'
But Babacan said that “we need more than words. We said that preventing the PKK from using Iraqi soil, an end to logistical support and all PKK activities inside Iraq and closing of its camps are needed. We also said its leaders need to be arrested and extradited to Turkey.”

During the funerals Tuesday of 12 soldiers slain by rebels in the weekend ambush, tens of thousands mourners chanted slogans urging the government to order an incursion.

Adding to the tension is the apparent capture of eight Turkish soldiers who have been missing since Sunday’s ambush.

Roj TV, a pro-Kurdish station that is based in Denmark and banned in Turkey on grounds that it is a mouthpiece for Kurdish rebels, aired footage of what it said were soldiers in rebel hands. In the footage, the camera pans across eight men standing in a row in the mountains with a PKK flag as a backdrop.